1. Field of the Invention
This invention relates to ski poles. More particularly, it relates to collapsible ski poles that can be shortened when out of use, for more convenient storage or shipping.
2. The Prior Art
Ski poles customarily have a hand grip at one end and a laterally extending snow basket at the other end. The hand grip usually has various lateral structures that can provide means to hold the ski pole securely and sometimes include a support or hand guard to take downward pressure from the skier's hand. These gripping structures also usually include a wrist strap.
It is desirable for a ski pole to be both collapsible for storage and shipping, and adjustable in length to enable skiers of different heights, for example, the members of a family, to share the same poles. Such adjustability enables the pole to "grow" with a child, and can reduce stocking requirements for retailers and rental sites: there is no need to stock many different sizes. Adjustability is thus a valuable and important characteristic, and as the prior art shows, there has been a long-felt need for, and many attempts have been made to provide, a satisfactory adjustable ski pole.
Telescopic ski poles are known, for example from U.S. Pat. Nos. 2,275,330; 2,289,818; 2,494,878; 3,712,652; 3,722,903; 3,730,544; 4,288,102; 4,424,987 and 4,596,405. While telescopic means are effective in rendering the out-of-use pole more compact, they suffer important drawbacks and are inconvenient. An out-of-use telescoping pole, such as those shown in the above-referenced patents, has encumbrances at both ends, in the form of the hand grip at one end and the basket at the other end. Alternatively, those constructions where the sections are separable, suffer the awkwardness of providing multiple freely movable sections that may be hard to control, especially with one hand, and quite difficult to store.
Several of the above-referenced disclosures show a telescopic ski pole that is adjustable to a limited number of locked or located positions to enable a skier to choose a comfortable pole length. Indeed, it can be considered to be a customary teaching in the art to use a telescopic mechanism to provide both collapsibility and adjustability.
What is lacking from all the prior art proposals that are known to the applicant (who went to the expense of commissioning a professionally conducted search for the purpose) is a full appreciation of the demands placed on its construction by normal use of the ski pole. In use a ski pole is often pounded into snow or ice, and may well strike hidden rocks quite violently, subjecting the pole to very substantial stresses which can soon destroy complex and delicate structures.
Telescopic mechanisms respond poorly to such treatment, their tubes are liable to deform, their latching or locking components are liable to strip, producing a sloppy, potentially dangerous mechanism. These problems are exacerbated by structures which tend to divert downward pressures laterally. Telescopic ski poles are thus not very durable and their popularity is limited.
In an unrelated art, U.S. Pat. No. 3,655,297 to Bolen Jr. et al discloses a foldable paddle with a hinge assembly at its mid-point. The paddle is not adjustable so that its structure does not help meet the objectives of the present invention. Furthermore, the complex hinge structure of Bolen Jr. et al with its thin, plate-like links does not help overcome the drawbacks of telescopic ski poles because it is designed to resist bending stress in the direction of paddling, not downward or lengthwise stresses. In response to sudden, heavy downward loads, the Bolen hinge structure with its plate-like links is subject to flexure and weakening. The use of such a structure for ski poles is plainly contra-indicated as providing no apparent benefit and being impracticable.
U.S. Pat. No. 3,730,544 to Hyman discloses a collapsible and foldable ski pole formed in three interfitting sections strung or tethered together by a flexible cable. When collapsed, the folded ski pole of Hyman is also encumbered by hand grip structures at one end and a snow basket at the other and is thus inconvenient. Nor is Hyman adjustable. Hyman thus cannot meet the objectives of the present invention.
U.S. Pat. No. 4,332,399 to Kepple discloses a ski pole having separable sections connected by a coil spring which provides limited lateral flexure of the assembled pole, under stress. The out-of-use pole suffers the drawback of the separable telescoping poles, namely multiple freely movable sections that are hard to control and stow. How successfully it transmits downward loads is not clear and will depend upon the particular spring construction. In any event, Kepple is not adjustable and therefore lacks the flexibility of use which constitutes one of the objectives of the present invention.